Work back through a story
Use the ending amount to find an earlier amount or a missing change.
Explore this lesson →6 practice questions · Optional read aloud · Thinking pad
Let’s understand the idea.
- The first event in the story is not always the first calculation you can do.
- Find a relationship with one missing amount. Undo an arrival by subtracting; undo a departure by adding back.
- Use the amount you found in the other relationship. Check both events in their original order.
Something to notice
Ask the learner to retell a new story, draw their own model and justify each equation. The provided maps scaffold representation; correct entries alone do not establish independent modeling or reading comprehension. Discuss other valid methods and check the answer in the original story.
Try it. Change it. Explain it.
Open the lesson to use its pictures and controls. In How it works, connect the picture to the idea. In Play & discover, change the quantities and notice what stays the same. In Your turn, answer questions and use the explanation to check your reasoning.
You can ask for help, draw on the thinking pad, or listen to the question and answer options. Progress distinguishes independent work from work completed with help.
Let’s try it →Curriculum connection
Grade 2 · 2.OA · US Common Core
This lesson is mapped to these standards. A completed activity is practice evidence, not a claim of mastery. Content is checked against the linked official standards and its mathematical models are tested.